33. THE SYCAMORE AND HORSE CHESTNUT.
1. The sycamore.—Observe the size and general shape of the tree. Examine the twigs in winter and watch the buds open in spring. Draw a leaf. Why are the leaves usually so sticky in warm weather? Notice the hanging sprays of green flowers. Are both stamens and pistil present in the same flower? Are the flowers visited by bees? Why? Follow the development of the fruit. Draw a pair of fruits. What is the use of the wing on a fruit? Do the fruits fall off themselves or are they torn off by gales? Look for seedling sycamores in the woods; also germinate seeds in garden soil and again observe the various stages.
Compare the plane, and notice the pyramidal shape of the tree. The leaves are very similar in outline to those of the sycamore, but the flowers are clustered into balls which dangle on long stalks. In summer, pull off a leaf and observe how the axillary bud is covered by the cup-shaped base of the leaf-stalk.
2. The horse chestnut.—Notice the general shape and method of branching. These characters, the large buds in winter, and the shape and size of the leaves in spring and summer, render the tree easily recognisable at all seasons. Trace the connection between the method of branching and arrangement of the leaves and buds on the twigs. Note the date of flowering, and of the unfolding and shedding of the leaves. Examine the flowers; are they pollinated by insects or by the wind? Trace the development of the fruit.
Fig. 128.—The Sycamore.
The sycamore ([Fig. 128]) is one of the best-known trees in this country, and often grows to a great height. Its leaves ([Fig. 33]) are large and five-pointed, the main veins spreading from the top of the leaf stalk. When young they are of a beautiful red colour. In hot weather the leaves become very sticky with a sugary syrup called honey-dew. The sycamore is indeed a species of maple, and is closely related to the sugar maple of North America. In May, the flowers hang from the twigs in drooping green clusters. They contain both stamens and pistils, and are visited by bees for the sake of the honey in which they abound. The fruits or keys (Figs. [ 137] and [ 4]) occur in pairs, or sometimes three together. Each has a flat, membranous wing, by means of which it is easily transported by the wind.
In Scotland the sycamore is often called the plane. The leaves of the plane and sycamore are somewhat similar in shape, but the trees belong to different families. The plane can be identified by its globular heads of flowers and subsequent balls of seeds, which hang on long stalks from the twigs.